Apparatus for making abrasive articles



De@ 1s, 1945.

E. VAN DER PYL APPARATUS'FOR MAKING ABRASIVE ARTICLES Filed July 23,V 1942 j .1* ,m A Q. H 1% ,m m am www@ EDWARD WN .DER F'Yl..

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Patented Dec. 18, 1945 APPARATUS FOR MAKING ABRASIVE ARTICLES 'Edwardvvan der Pyl, Holden, Mass., assignor to Norton Company, Worcester,

tion of Massachusetts Application July 23, 1942, Serial No. 452,009

s claims. (c1. aol-zes) This invention relates to a method of and apparatus for making abrasive articles and with regard to its more specific features to the fixing of diamond abrasive grains, preferably in a single layer, on a suitable backing. An object of the invention is to provide a simple, practical and eiilcient method and apparatus for the manufacture of vabrasive articles.

Another object is to provide for .the dependable attachment or mountingof abrasive particles to a metallic or other conductive support without the use of an organic or other cement,

in a manner to meet reliably the requirements of practical'use.

a practical, easily operated, and inexpensive means for mutuallypositioning and holding together an article and abrasive grains which are to be assembled to form the abrasive article.

Another object of the invention is to provide a dependable means to effect close and even dispersion or distribution of the abrasive granules relative to the selected backing or support.

Other objects will be in part obvious orvin part pointed out hereafter. f l 'I 'he invention accordingly consists in thefeatures of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of said steps to one or more of the others thereof, all as will be pointed out in the following description, and the scope of the -application of which will be indicated in the following claims. y

In the accompanying drawing illustrating one of various possible embodiments of the mechanical features of the invention,

Figure 1 is a top plan view of apparatus for carrying out my invention;

Figure 2 is across sectional view on an enlarged scale'as seen along the line 2-2 of Fig,

ure 1, certain parts being 'shown in front elevation;

Figure 3 is a detached vertical sectional viewy Mass., a corpora- Figure 4 is a horizontal sectional view taken on the line I-I 'of Figure 3;

Figure 5 is a detached vertical sectional view of a device or collet for releasably engaging and holding assembled the support and abrasive grain container; f

Figure 6 is a side elevation, partly in section, of funnel means for supplying abrasive grains to the container;

Figure '1 is an end view of the funnel as seen from thev right in Figure 6;

Figure 8 is a side elevation of the finished abrasive article, illustrated in the form of a dental point having a frusto-conical operative portion supporting the abrasive grains; and

Figure 9 is a fragmentary central cross section on a greatly enlarged 'scale of the operative portion of the dental point of Figure 8, to show better the relation between-the support and the abrasive grains.

Similar reference characters refer to similar parts throughout the several views.

Let it be assumed for purposes of illustration that the abrasive article to be made is a so-called dental point; it comprises a metal shank I0 and a portion II that is to be covered with abrasive grains. Such an illustrative backing, or support for'abrasive grains, I mount in any suitable support I2 and arrange to relate with porous means I3, formed of material, such, for example, as porous refractory material, pervious to an electro-plating solution in which the porous means is positioned asl will be explained, and spaced from the backing II to receive abrasive grains 60 between it and the backing II. The means I3 serves as retaining means holding the backing Il and the mass of abrasive grains 60 in mutual contact while plating metal is being deposited upon the backing Ii, thereby building up a metal matrix encompassing the vabrasive grains positioned against or adjacent tothe surface of the backing. The form of the porous retaining means I3 and the means for supporting the blank to be coated with abrasive grains may, of course, be widely varied in accordance with the requirements of the particular backing to which the abrasive grain is to be fixed. In the specific illustration given herein, the means for supporting a dental point blank consists of a holder I2 at the lower end of a shaft I4 extending through and supported from, as by screw threads I5, an inverted cup-shaped support member I6, said shaft I4 being'counter-bored' at its lower end at I1 to receive the rear end .or shank I0 of said dental point blank. The annuremoved therefrom sufficiently to provide a chamber, the inner wall of which is the surface to .be coated, I provide porous means I3 forming the outer wall of said chamber and thus serving to compact the abrasive granules with which the chamber is lled and to hold the inner layer of said granules and the back II in mutual contact. In the specific illustration given herein, the porous means I3 is in theform of a hollow container,

the lower portion 20 of which ispreferably shaped to conform to the shape of the article to be coated with abrasive whereby the combined thickness of the layer of abrasive surrounding the surface of back II plus the surrounding wallI of container I3 will be uniform thus facilitating an even electro-deposition of plating metal on all portions of back II as will be more fully explained. The upper portion 2| of container I3 is substantially cylindrical and is adapted to be recived and held by spring fingers 22 of an inverted cup-shaped collet-like member 23. which is secured on shaft I4, preferably integrally therewith, and is adapted to fit within the cup-shaped member I6. The spring fingers 22 may be formed by dividing the annular wall 24 of member 23, as by the vertically extending spaced slots 25. Thus in the specific embodiment of the invention ldescribed herein when the shank I of a dental point blank is inserted in its holder I2, comprising the lower end of shaft I4, and these members are assembled with container I3, the portion II of the dental point blank projects into the hollow interior of the lower portion 20 of said container I3 and there is thus formed an annular chamber 26, the inner wall of which is the frustoconical surface of said portion II, and the outer wall. of which is the porous wall of container I3. The said annular chamber 23 being of uniform cross section it will be apparent that when abrasive granules 60 are introduced into the said chamber all portions of thesurface of portion II will be covered to an equal depth with abrasive grains which will be evenly and closely distributed over the surface of portion Il, and the inner layer of said abrasive grains so distributed will be held in physical contact with the surface of portion II through the action of the remainder of the mass of abrasive grains and the porous retaining means, constituted by the wall of chamber I3 in the specific embodiment of the invention illustrated herein. It will also be noted that all portions of the surface of portion II are substantially equally spaced from the outer surface of the wall of container I3.

Communicating with chamber 26 are the more or less vertically extending passageways 21 which at their upper ends respectively are flared outwardly at 28 to register with passageways 29, extending through the horizontal wall of cupshaped support member I6, through ports 30 in the horizontally extending portion of the cupshaped member23. If desired, to facilitate supplying granules to chamber 2E, funnel means 3I may be -inserted in the passageways 29, through ports 30, with the lower end of said funnel mefn in registry with the outwardly flared upper ends 23 of passageways 21.

At its upper end cup-shaped support member IB is provided with a laterally extending annular flange 32 by which the assembly comprising support I3, shaft I4 with its cup-shaped holder 23 for container I2. and container I2, may be conveniently suspended in an electro-plating bath chamber, as by resting on the top 33 of a receptacle 34 containing an electro-plating solution 35, the top 33 being bored to permit insertion therethrough of the body of holder I6 and the container assembly.

The porous retaining means, which in the illustrative embodiment of the invention described herein is the container I3, is immersed in the electrolyte 35, preferably to a level slightly above the top of the back to be coated with plating metal as indicated at 33, Figures 1 and 3. Plating metal is supplied from anode means 31, which may be formed of any suitable metal for plating, preferably a soft strong metal such as copper, chromium, or nickel. The anode means preferred for the specific embodiment of the invention described herein consists of a number of anodes 31 also immersed in the electrolyte 35 and equally spaced from one another and from the surface of back II. This arrangement of the anodes 31 resuits, in the case of the specic embodiment of the invention illustrated herein, in the disposition of the anode members 31 at evenly spaced vintervals around the periphery of a circley concentric withthe axis 0f the frusto-conical back I I, and inclined at an angle corresponding to the taper of the surface of back I I and the surrounding portion of the wall of vcontainer I3. The anodes 31 are attached at their upper ends respectively in any suitable way, by welding, for example, or by solder 38 as illustrated herein, to the posts 39 formed of any suitable metal, preferably brass, Which extend through bores in the top 33 and are screw-threadedly engaged as at 4I in collars 40 which rest upon the receptacle top 33. The posts 39 may also be provided with annular 7 flanges 42 adapted to rest against the lower sur..

face of top 33 to prevent upward movement of the posts 39 and to cooperate with collars 40 in securely positioning the posts 39 respectively.

The upper end of holder shaft I4 is bored radially at 43 for connection to electrical conductor 45 leading tothe negative pole of a source of electrical energy and has a bore 44. extending vertically from itsupper end to the radial bore 43, in which a thumb screw 46 may be adjustably seated to press upon and positively engage the` end of the said conductor inserted in bore 43 as indicated in Figure 3. Similarly each of the posts 39 is provided adjacent its upper end with a radial bore 49 for connection to conductor 5I leading to the positive pole of said source of electrical energy and has a bore at 50 extending vertically from its upper end to the radial bore 49 in which a thumb screw 52 may be adjustably seated to press upon and :positively engage the said conductor, as indicated in Figure 1.

It will thus be seen that the anodes 31 are connected to the positive end of an electro-plating circuit and the backing II to be coated with abrasive granules, which as illustratively disclosed herein .is the frusta-conical surface of a dental point blank, is connected through the metal shaft I4 and its holder end I2, with the negative end of an electro-plating circuit, thus constituting cathode means on which the plating metal is deposited from the electrolyte 35 peneaseneoe trating the pervious wall of abrasive retaining member I3. and the mass of granules when the electro-plating circuit is energized.

It will be understood that the arrangement of the anodes 31 in equally spaced relation to the back II tends to provide uniform current density in the portion of the electrolyte contacting the 'porous member I3 and passing throughvmember I3 into contact with back II, to insure a uniform rate of electro-deposition of the plating metal on all portions of back I'I. It will also be readily .'understcod that when the space between the porous retaining member I3 and the back II to be coated with abrasive granules is filled with abrasive granules 60 the electrolyte penetrating abrasive granules to a height determined by the character of the electrolyte solution and the period of the plating operation, and thereby forml ing' a matrix positively and firmly embedding thev abrasive granules and binding them to the'back lWhile preferably the v:plating operation will be continued only long enough to bind a single layer of abrasive granules -to the surface of backv I I it will beunderstood that, if desired, the electro-depositing of plating metal may be continued until the accretion on back II encompasses a second-or further layer of abrasive granules of a mass of abrasive granules interposed lbetween the back II- and the porous retaining member I3,

thereby providing an abrasive coating of any desired depth.

The receptacle 34 'and its top 33 may be of any suitable material but is preferably mad-e of Pyrex glass. Preferably the top 33 of receptacle 34 is vbored at 41 and have a cross pin 48 inserted in bore 41 to serve `as aI hand piece to -give leverage in screwing or unscrewing the shaft I4 andthe cup-shaped holder I6.

The container I3, shown herein as illustrative of porous means for retaining abrasive granules against a backing tobe coated with the granules, preferably comprises an inner annular two-part portion 55 divided as for example along line 56 into the halves 55a and 55h, and an outer annular portion 51, concentric with the said inner portion when the parts 55a and 55h. are assembled. Outer portion 51 is adapted when inserted in collet-like cup-shaped support member I6 to hold inner annular portion members 55a and 55h firmly around the lower end of shaft I4 and particularly around the shank III of the dental point just above the frusto-conical or back por-l tion II and against the base thereof, providing a closure to prevent coating of the'shank.

Any suitable metal may be used for plating. I

However, a strong metal which will produce a strong coating is desired. The dental point Vink portion II, illustrated herein asthe back to be coated. may be made out of German silver and in such eases the anodes 31 may be nickel. In many cases it is desired to produce a coating of abrasive upon a steel back and in such cases the anode means .may be nickel or desirably chromium. The yelectrolyte 35- will, of course,

be selected in accordance with the particular metal being used to plate. l For plating with nickel, a nickel sulphate formula, may be used.

10 The following formulae may be used:

TABLE I Warm nickel (Watts type) y Single nickel salt..` oz'./gal- 25-45 Nickel chloride oz./gal 6-9 Boric acid oz./gal 4-6' pH Colorimetric s 5.2-5.8 Temperature ....v.-.. -F. 120-160 Current density amp/sq. ft-- 15-50 f o For chromium plating the following solution can be used:

TABLE II Chromium plating 2 Chromic acid. f oz./gal 40 Sulfuric acid --oz./gal .40 Chromic acid/sulphate ratio 100-75 Temperature F 115-140 Current density amp./sq. ft-- 100-600 The electric current density used for nickel plating may suitably be from 25 to 40 amperes per square foot. For chromium plating a higher density, on the order of 100 amperes per square foot, or more, may be used.

In all cases it is desirable to work on the low side of the current density tables. In this way a stronger plating is achieved. i

The grit size of the abrasive used may be widely varied according to the body to which the coating is applied and the grinding characteristics desired to be obtained. In the above illustration of the embodiment of the invention, diai mond grains having a grit size of 150 mesh may be employed.-` The thickness of the coating of plated metal deposited is preferably more than one-half, say, from one-half to slightly more than three-quarters of, the radial thickness of the diamond granules from the surface of back II, and in the specic embodiment of the invenl tion given herein, will be on the order of from two to three thousandths of an' inch. /For electro-depositing a plating metal to approximately such depth on a back, such as the frusto-conivided by this invention a method, apparatus, and

an article in which the various objects hereinv above kset forth together with many thoroughly practical advantagesv are successfully achieved. As various possible embodiments might be made of the mechanical features of the above invention and as the art herein described might be Vcal portion of the dental point selected herein to l illustrate a practical application of the invention,

varied in various parts, all without departing from the scope of the invention, it is to be understood that al1 matter hereinbefore set forth or shown in the accompanying drawing is to be lnterpreted as illustrative and not in a limiting sense.

What I claim is:

l. In combination with, a cup-shaped support-member adapted to be lpositioned above an electroplating bath, with its open end extending toward the bath, a cathode member extending through the closed end of said cup-shaped support member and having means adjacent its lower end to support a blank, said cathode member having a cup-shaped portion adapted to flt within said cup-shaped support and forming a collet, a porous container, having an outer annular portion adapted to be spring-ntted into said collet and to surround the lower end of said cathode member and the blank supported thereby and to provide a space between said outer portion and said blank, and an inner annular portion divided into a plurality of parts-and adapted to provide a shield around the lower end of the cathode member and to be held rmly against said cathode member by the said outer annular portion of said container when the latter is inserted in said collet, and means for introducing granules into said container between the inner and outer annular portions of said container `and into said space between said outer portion and said blank.

2. Apparatus for makingv abrasive articles comprising a holder for a metal blank, having a depending flange extending concentrically therearound and forming a collet, and a porous receptacle having a portion adapted to be spring tted into said colletand having a portion adapted to enclose said holder andto provide a space between its wall and a blank positioned therein by said holder, said holder and said receptacle having complementary passageway/s through which abrasive granules may be introduced into the said porous receptacle and interposed be'- tween said blankand the porous wall of said receptacle.

3. In apparatus for xing abrasive granules on a backing electrolytically, a porous receptacle adapted to be vsuspended in an electroplating bath, a cathode member extending into said porous receptacle and having means for supporting a metal blank within said receptacle in spaced relation tothe wall of the receptacle, means for introducing abrasive granules into said porous receptacle and around the portion of said blank to which it is desired to amx the abrasive granules, and means supported in said porous receptacle for shielding another portion of said blank from contact with said granules, and, from the plating action of an electroplating bath in which said porous receptacle is suspended. l

EDWARD VAN DER PYL. 

